I am the owner of that 92 Crown Vic. After I replaced the oil filter
mounting block gasket, which took care of the external oils leaks, I was
driving the car up to a funeral in PA. The car got its usual great
highway milage - between 20 and 23 MPG, depending on driving conditions,
etc. When I got up to PA, I got stuck in traffic on I-81 around
SCranton while on the way to a funeral home and decided to take a detour
through town. I headed into dwontown Scranton and hit a pothole and the
car went from being a quiet sedan to sounding like a NASCAR racer. WHen
I was able to stop and take a look, the Y-pipe cracked right in front of
I took it to a muffler shop the next day, and they fixed it right up.
They used a torch to melt the rusted old bolts off the clamps, then had
to expand the pipe at the muffler to accomodate the new pipe. Then the
mechanic went at the flanges behind each of the convertors with a ball
peen hamer to clean off the old gaskets - which made me grimmace because
I thought that might not have been good for the cat or the O2 sensor.
Then they hammered at the back of the muffler to get the Y-pipe to fit
into the pipe at the front of the muffler. The car was quiet again, but
I noticed over the rest of the trip that the milage had gone down - now
that I am home again, the milage is under 18-19 MPG. Now I did put on a
new PCV valve and wasn't able to check the larger of the two vaccuum
lines from the PCV valve to what I presume is the vaccuum manifold to
see if it was clogged. I haven't driven enough miles to see if the oil
has leaked out.
But I wonder why my MPG has gone down since getting the new pipe
installed? Could the hammering have messed up the original cat -
perhaps damaging the mesh in the cat body? Or did running the car with
no muffler for over a day mess up the O2 sensors?